Complex tracer mobilities in polymer networks revealed by fluorescence correlation spectroscopy

Gels are elastic porous polymer networks that are accompanied by pronounced mechanical properties. Due to their biocompatibility, ‘responsive hydrogels’ (HG) have many biomedical applications ranging from biosensors and drug delivery to tissue engineering. They respond to external stimuli such as temperature and salt by changing their dimensions. Of paramount importance is the ability to engineer penetrability and diffusion of interacting molecules in the crowded HG environment, as this would enable one to optimize a specific functionality. Even though the conditions under which biomedical devices operate are rather complex, a bottom-up approach could reduce the complexity of mutually coupled parameters influencing tracer mobility. The present thesis focuses on the interaction-induced tracer diffusion in polymer solutions and their homologous gels, probed by means of Fluorescence Correlation Spectroscopy (FCS). This is a single-molecule-sensitive technique having the advantage of optimal performance under ultralow tracer concentrations, typically employed in biosensors. Two different types of hydrogels have been investigated, a conventional one with broad polydispersity in the distance between crosslink points and a so-called ‘ideal’, with uniform mesh size distribution. The former is based on a thermoresponsive polymer, exhibiting phase separation in water at temperatures close to the human body temperature. The latter represents an optimal platform to study tracer diffusion. Mobilities of different tracers have been investigated in each network, varying in size, geometry and in terms of tracer-polymer attractive strength, as perturbed by different stimuli. The thesis constitutes a systematic effort towards elucidating the role of the strength and nature of different tracer-polymer interactions, on tracer mobilities; it outlines that interactions can still be very important even in the simplified case of dilute polymer solutions; it also demonstrates that the presence of permanent crosslinks exerts distinct tracer slowdown, depending on the tracer type and the nature of the tracer-polymer interactions, expressed differently by each tracer with regard to the selected stimulus. In aqueous polymer solutions, the tracer slowdown is found to be system-dependent and no universal trend seems to hold, in contrast to predictions from scaling theory for non-interacting nanoparticle mobility and empirical relations concerning the mesh size in polymer solutions. Complex tracer dynamics in polymer networks may be distinctly expressed by FCS, depending on the specific synergy among-at least some of - the following parameters: nature of interactions, external stimuli employed, tracer size and type, crosslink density and swelling ratio.

Impact of anthropogenic stressors on the population genetics of the common bioindicator Dreissena polymorpha (Pallas, 1771)

Toxicant inputs from agriculture, industry and human settlements have been shown to severely affect freshwater ecosystems. Pollution can lead to changes in population genetic patterns through various genetic and stochastic processes. In my thesis, I investigated the impact of anthropogenic stressors on the population genetics of the zebra mussel Dreissena polymorpha. In order to analyze the genetics of zebra mussel populations, I isolated five new highly polymorphic microsatellite loci. Out of those and other already existing microsatellite markers for this species, I established a robust marker set of six microsatellite loci for D. polymorpha. rnMonitoring the biogeographical background is an important requirement when integrating population genetic measures into ecotoxicological studies. I analyzed the biogeographical background of eleven populations in a section of the River Danube (in Hungary and Croatia) and some of its tributaries, and another population in the River Rhine as genetic outgroup. Moreover, I measured abiotic water parameters at the sampling sites and analyzed if they were correlated with the genetic parameters of the populations. The genetic differentiation was basically consistent with the overall biogeographical history of the populations in the study region. However, the genetic diversity of the populations was not influenced by the geographical distance between the populations, but by the environmental factors oxygen and temperature and also by other unidentified factors. I found strong evidence that genetic adaptation of zebra mussel populations to local habitat conditions had influenced the genetic constitution of the populations. Moreover, by establishing the biogeographical baseline of molecular variance in the study area, I laid the foundation for interpreting population genetic results in ecotoxicological experiments in this region.rnIn a cooperation project with the Department of Zoology of the University of Zagreb, I elaborated an integrated approach in biomonitoring with D. polymorpha by combining the analysis techniques of microsatellite analysis, Comet assay and micronucleus test (MNT). This approach was applied in a case study on freshwater contamination by an effluent of a wastewater treatment plant (WWTP) in the River Drava (Croatia) and a complementary laboratory experiment. I assessed and compared the genetic status of two zebra mussel populations from a contaminated and a reference site. Microsatellite analysis suggested that the contaminated population had undergone a genetic bottleneck, caused by random genetic drift and selection, whereas a bottleneck was not detected in the reference population. The Comet assay did not indicate any difference in DNA damage between the two populations, but MNT revealed that the contaminated population had an increased percentage of micronuclei in hemocytes in comparison to the reference population. The laboratory experiment with mussels exposed to municipal wastewater revealed that mussels from the contaminated site had a lower percentage of tail DNA and a higher percentage of micronuclei than the reference population. These differences between populations were probably caused by an overall decreased fitness of mussels from the contaminated site due to genetic drift and by an enhanced DNA repair mechanism due to adaptation to pollution in the source habitat. Overall, the combination of the three biomarkers provided sufficient information on the impact of both treated and non-treated municipal wastewater on the genetics of zebra mussels at different levels of biological organization.rnIn my thesis, I could show that the newly established marker set of six microsatellite loci provided reliable and informative data for population genetic analyses of D. polymorpha. The adaptation of the analyzed zebra mussel populations to the local conditions of their habitat had a strong influence on their genetic constitution. We found evidence that the different genetic constitutions of two populations had influenced the outcome of our ecotoxicological experiment. Overall, the integrated approach in biomonitoring gave comprehensive information about the impact of both treated and non-treated municipal wastewater on the genetics of zebra mussels at different levels of biological organization and was well practicable in a first case study.

Prediction of hip and hand fractures in older persons with or without a diagnosis of periodontitis

Purpose: In a prospective study, we assessed if a diagnosis of osteoporosis and periodontitis could predict hip and hand fractures in older persons. Materials and methods: Bone density was assessed by a Densitometer. Periodontitis was defined by evidence of alveolar bone loss. Results: 788 Caucasians (52.4% women, overall mean age: 76 years, S.D. +/- 9.0, range: 62 to 96) were enrolled and 7.4% had a hip/hand fracture in 3 years. Calcaneus PIXI T-values < - 1.6 identified osteoporosis in 28.2% of the older persons predicting a hip/hand fracture with an odds ratio of 3.3:1 (95% CI: 1.9, 5.7, p < 0.001). Older persons with osteoporosis had more severe periodontitis (p < 0.01). Periodontitis defined by >= 30% of sites with >= 5 mm distance between the cemento-enamel junction (CEJ) and bone level (ABL) was found in 18.7% of the older persons predicting a hip/hand fracture with an odds ratio of 1.8:1 (95% CI: 1.0, 3.3, p < 0.05). Adjusted for age, the odds ratio of a hip/hand fracture in older persons with osteoporosis (PIXI T-value <-2.5) and periodontitis was 12.2:1 (95% CI: 3.5, 42.3, p < 0.001). Conclusions: Older persons with osteoporosis and periodontitis have an increased risk for hip/hand fractures

Socio-Spatial Relationships in Dairy Cows

Farm animals may serve as models for evaluating social networks in a controlled environment. We used an automated system to track, at fine temporal and spatial resolution (once per minute, +/- 50 cm) every individual in six herds of dairy cows (Bos taurus). We then analysed the data using social network analyses. Relationships were based on non-random attachment and avoidance relationships in respect to synchronous use and distances observed in three different functional areas (activity, feeding and lying). We found that neither synchrony nor distance between cows was strongly predictable among the three functional areas. The emerging social networks were tightly knit for attachment relationships and less dense for avoidance relationships. These networks loosened up from the feeding and lying area to the activity area, and were less dense for relationships based on synchronicity than on median distance with respect to node degree, relative size of the largest cluster, density and diameter of the network. In addition, synchronicity was higher in dyads of dairy cows that had grown up together and shared their last dry period. This last effect disappeared with increasing herd size. Dairy herds can be characterized by one strongly clustered network including most of the herd members with many non-random attachment and avoidance relationships. Closely synchronous dyads were composed of cows with more intense previous contact. The automatic tracking of a large number of individuals proved promising in acquiring the data necessary for tackling social network analyses.

Efficient and Accurate Characterization of the Bergman Cyclization for an Expanded Substructure of Esperamicin A1

Incorporation of enediynes into anticancer drugs remains an intriguing yet elusive strategy for the design of therapeutically active agents. Density functional theory was used to locate reactants, products, and transition states along the Bergman cyclization pathways connecting enediynes to reactive para-biradicals. Sum method correction to low-level calculations confirmed B3LYP/6-31G(d,p) as the method of choice in investigating enediynes. Herein described as MI:Sum, calculated reaction enthalpies differed from experiment by an average of 2.1 kcal·mol−1 (mean unsigned error). A combination of strain energy released across the reaction coordinate and the critical intramolecular distance between reacting diynes explains reactivity differences. Where experimental and calculated barrier heights are in disagreement, higher level multireference treatment of the enediynes confirms lower level estimates. Previous work concerning the chemically reactive fragment of esperamcin, MTC, is expanded to our model system MTC2.

Should intentional endovascular stent-graft coverage of the left subclavian artery be preceded by prophylactic revascularisation?

Thoracic endovascular aortic repair (TEVAR) has emerged as a promising therapeutic alternative to conventional open aortic replacement but it requires suitable proximal and distal landing zones for stent-graft anchoring. Many aortic pathologies affect in the immediate proximity of the left subclavian artery (LSA) limiting the proximal landing zone site without proximal vessel coverage. In patients in whom the distance between the LSA and aortic lesion is too short, extension of the landing zone can be obtained by covering the LSA's origin with the endovascular stent graft (ESG). This manoeuvre has the potential for immediate and delayed neurological and vascular symptoms. Some authors, therefore, propose prophylactic revascularisation of the LSA by transposition or bypass, while others suggest prophylactic revascularisation only under certain conditions, and still others see no requirement for prophylactic revascularisation in anticipation of LSA ostium coverage. In this review about LSA revascularisation in TEVAR patients with coverage of the LSA, we searched the electronic databases MEDLINE and EMBASE historically until the end date of May 2010 with the search terms left subclavian artery, covering, endovascular, revascularisation and thoracic aorta. We have gathered the most complete scientific evidence available used to support the various concepts to deal with this issue. After a review of the current available literature, 23 relevant articles were found, where we have identified and analysed three basic treatment concepts for LSA revascularisation in TEVAR patients (prophylactic, conditional prophylactic and no prophylactic LSA revascularisation). The available evidence supports prophylactic revascularisation of the LSA before ESG LSA coverage when preoperative imaging reveals abnormal supra-aortic vascular anatomy or pathology. We further conclude that elective patients undergoing planned coverage of the LSA during TEVAR should receive prophylactic LSA transposition or LSA-to-left-common-carotid-artery (LCCA) bypass surgery to prevent severe neurological complications, such as paraplegia or brain stem infarction.

Placement of coiled catheters into the paravertebral space

There are conflicting results with regard to the use of catheter-based techniques for continuous paravertebral block. Local anaesthetic spread within the paravertebral space is limited and the clinical effect is often variable. Discrepancies between needle tip position and final catheter position can also be problematic. The aim of this proof-of-concept study was to assess the reliability of placing a newly developed coiled catheter in human cadavers. Sixty Tuohy needles and coiled catheters were placed under ultrasound guidance, three on each side of the thoracic vertebral column in 10 human cadavers. Computed tomography was used to assess needle tip and catheter tip locations. No catheter was misplaced into the epidural, pleural or prevertebral spaces. The mean (SD) distance between catheter tips and needle tips was 8.2 (4.9) mm. The median (IQR [range]) caudo-cephalad spread of contrast dye injectate through a subset of 20 catheters was 4 (4-5[3-8]) thoracic segments. All catheters were removed without incident. Precise paravertebral catheter placement can be achieved using ultrasound-guided placement of a coiled catheter.

An anatomical investigation of the cervicothoracic ganglion

Anatomical variability within the autonomic nervous system has long been accepted. This study evaluated the anatomical variability of the cervicothoracic ganglion (CTG) according to its form and, in addition, provided precise measurements between the CTG and the anterior tubercle of the transverse process of the sixth cervical vertebra (C6TP), the first costovertebral articulation, and the vertebral artery. Forty-two adult cadavers were dissected, 22 male and 20 females. Five main forms of CTG were documented; spindle (31.9%), dumbbell (23.2%), truncated (21.7%), perforated (14.5%), and inverted-L (8.7%). The means for length, width, and thickness of the CTG were 18.5 mm, 8.2 mm, and 4.5 mm, respectively. The dimensions were found to be slightly larger in the males than females and on the left sides as compared to the right. The mean shortest distance between the CTGs and the vertebral artery was found to be 2.8 mm, whilst the mean shortest distances to C6TP was 25.7 mm and to the first costovertebral articulation was 1.7 mm. There is great variability in the morphology of the CTG with five common forms consistently seen. The relation to the vertebral artery may influence the form of the ganglion. Two previously undocumented forms are recorded; the truncated which describes the important juxtaposition of the CTG and the vertebral artery and the perforated which describes the piercing of the ganglion itself by the artery. The findings are considered to be of clinical importance to anesthetists, surgeons, neurosurgeons, and anatomists.

Effect of immune pressure on hepatitis C virus evolution: insights from a single-source outbreak

The host's immune response to hepatitis C virus (HCV) can result in the selection of characteristic mutations (adaptations) that enable the virus to escape this response. The ability of the virus to mutate at these sites is dependent on the incoming virus, the fitness cost incurred by the mutation, and the benefit to the virus in escaping the response. Studies examining viral adaptation in chronic HCV infection have shown that these characteristic immune escape mutations can be observed at the population level as human leukocyte antigen (HLA)-specific viral polymorphisms. We examined 63 individuals with chronic HCV infection who were infected from a single HCV genotype 1b source. Our aim was to determine the extent to which the host's immune pressure affects HCV diversity and the ways in which the sequence of the incoming virus, including preexisting escape mutations, can influence subsequent mutations in recipients and infection outcomes. Conclusion: HCV sequences from these individuals revealed 29 significant associations between specific HLA types within the new hosts and variations within their viruses, which likely represent new viral adaptations. These associations did not overlap with previously reported adaptations for genotypes 1a and 3a and possibly reflected a combination of constraint due to the incoming virus and genetic distance between the strains. However, these sites accounted for only a portion of the sites in which viral diversity was observed in the new hosts. Furthermore, preexisting viral adaptations in the incoming (source) virus likely influenced the outcomes in the new hosts.

Bone dimensions in the posterior mandible: a retrospective radiographic study using cone beam computed tomography. Part 1--analysis of dentate sites

This retrospective radiographic study analyzed the dimensions of the alveolar bone in the posterior dentate mandible based on cone beam computed tomography (CBCT) images. A total of 56 CBCT images met the inclusion criteria, resulting in a sample size of 122 cross sections showing posterior mandibular teeth (premolars and molars). The thickness of the buccal and lingual bone walls was measured at two locations: 4 mm apical to the cementoenamel junction (measurement point 1, MP1) and at the middle of the root (measurement point 2, MP2). Further, alveolar bone width was assessed at the level of the most coronal buccal bone detectable (alveolar bone width 1, BW1) and at the superior border of the mandibular canal (alveolar bone width 2, BW2). The vertical distance between the two as well as the presence of a lingual undercut were also analyzed. There was a steady increase in buccal bone wall thickness from the first premolar to the second molar at both MP1 and MP2. BW1 at the level of the premolars was significantly thinner than that for molars. Alveolar bone height was constant for all teeth examined. For the selection of an appropriate postextraction treatment approach, analysis of the alveolar bone dimensions at the tooth to be extracted by means of CBCT can offer valuable information concerning bone volume and morphology at the future implant site.

Immediate restoration of nonsubmerged titanium implants with a sandblasted and acid-etched surface: five-year results of a prospective case series study using clinical and radiographic data

The aim of this study was to evaluate the survival and success rates of immediately restored implants with sandblasted, large-grit, acid-etched (SLA) surfaces over a period of 5 years. Twenty patients (mean age, 47.3 years) received a total of 21 SLA wide-neck implants in healed mandibular first molar sites after initial periodontal treatment. To be included in the study, the implants had to demonstrate primary stability with an insertion torque value of 35 Ncm. A provisional restoration was fabricated chairside and placed on the day of surgery. Definitive cemented restorations were inserted 8 weeks after surgery. Community Periodontal Index of Treatment Needs (CPITN) indices and the radiographic distance between the implant shoulder and the first visible bone-implant contact (DIB) were measured and compared over the study period. The initial mean CPITN was 3.24, and decreased over the study period to 1.43. At the postoperative radiographic examination, the mean DIB was 1.41 mm for the 21 implants, indicating that part of the machined neck of the implants was placed slightly below the osseous crest. The mean DIB value increased to 1.99 mm at the 5-year examination. This increase proved to be statistically significant (P < .0001). Between the baseline and 5-year examinations, the mean bone crest level loss was 0.58 mm. Success and survival rates of the 21 implants after 5 years of function were 100%. This 5-year study confirms that immediate restoration of mandibular molar wide-neck implants with good primary stability, as noted by insertion torque values of at least 35 Ncm, is a safe and predictable procedure.

Computerized tomographic morphometric analysis of the cervical spine

Detailed knowledge of cervical canal and transverse foramens' morphometry is critical for understanding the pathology of certain diseases and for proper preoperative planning. Lateral x-rays do not provide the necessary accuracy. A retrospective morphometric study of the cervical canal was performed at the authors' institution to measure mean dimensions of sagittal canal diameter (SCD), right and left transverse foramens' sagittal (SFD) and transverse (TFD) diameters and minimum distance between spinal canal and transverse foramens (dSC-TF) for each level of the cervical spine from C1-C7, using computerized tomographic scans, in 100 patients from the archives of the Emergency Room.

Metacommunity Dynamics Of Benthic Macroinvertebrates In A Large River

Metacommunity ecology focuses on the interaction between local communities and is inherently linked to dispersal as a result. Within this framework, communities are structured by a combination of in-site responses to the immediate environment (species sorting), stochasticity (patch dynamics), and connections to other communities via distance between communities and dispersal (neutrality), and source-sink dynamics (mass effects; see Chapter 1 for a detailed description of metacommunity theory, the study site, and macroinvertebrate communities found). In Chapter 2 I describe spatial scale of study and dispersal ability as both have the ability to influence the degree to which communities interact. However, little is known about how these factors influence the importance of all metacommunity dynamics. I compared dispersal mode of immature aquatic insects and dispersal ability of winged adults across multiple spatial scales in a large river. The strongest drivers of river communities were patch dynamics, followed by species sorting, then neutrality. Active dispersers during aquatic lifestages on average exhibited lower patch dynamics, higher species sorting, and significant mass effects compared to passive dispersers. Active and strong dispersers also had a scale-independent influence of neutrality, while neutrality was stronger at broader spatial scale for passive and weak dispersers. These results indicate as dispersal ability increases patch dynamics decreases, species sorting increases, and neutrality should decrease. The perceived influence of neutrality may also be dependent on spatial scale and dispersal ability. In Chapter 3 I describe how river benthic macroinvertebrate communities may influence tributary invertebrate communities via adult flight and tributaries may influence mainstem communities via immature drift. This relationship may also depend on relative mainstem and tributary size, as well as abiotic tributary influence on mainstem habitat. To investigate the interaction between a larger river and tributary I sampled mainstem benthic invertebrate communities and quantified habitat of a 7th order river (West Branch Susquehanna River) above and below a 5th order tributary confluence, as well as 0.95-3.2 km upstream in the tributary. Non-metric multidimensional scaling showed similar patterns of clustering between sampling locations for both habitat characteristics and invertebrate communities. In addition, mainstem river communities and habitat directly downstream of the tributary confluence cluster tightly together, intermediate between tributary and mid-channel river samples. In Bray-Curtis dissimilarity comparisons between tributary and mainstem river communities the furthest upstream tributary communities were least similar to river communities. Middle tributary samples were also closest by Euclidean distance to the upstream mainstem riffle and exhibited higher similarity to mid-channel samples than the furthest downstream tributary communities. My results indicate river and tributary benthic invertebrate communities may interact and likely result in direct and indirect mass effects of a tributary on the downstream mainstem community by invertebrate drift and habitat restructuring via material delivery from the tributary. I also showed likely direct effects of adult dispersal from the river and oviposition in proximal tributary locations where Euclidian, rather than river, distance may be more important in determining river-tributary interactions.

Ultrasound-guided blocks of the ilioinguinal and iliohypogastric nerve: accuracy of a selective new technique confirmed by anatomical dissection

BACKGROUND: Ilioinguinal and iliohypogastric nerve blocks may be used in the diagnosis of chronic groin pain or for analgesia for hernia repair. This study describes a new ultrasound-guided approach to these nerves and determines its accuracy using anatomical dissection control. METHODS: After having tested the new method in a pilot cadaver, 10 additional embalmed cadavers were used to perform 37 ultrasound-guided blocks of the ilioinguinal and iliohypogastric nerve. After injection of 0.1 ml of dye the cadavers were dissected to evaluate needle position and colouring of the nerves. RESULTS: Thirty-three of the thirty-seven needle tips were located at the exact target point, in or directly at the ilioinguinal or iliohypogastric nerve. In all these cases the targeted nerve was coloured entirely. In two of the remaining four cases parts of the nerves were coloured. This corresponds to a simulated block success rate of 95%. In contrast to the standard 'blind' techniques of inguinal nerve blocks we visualized and targeted the nerves 5 cm cranial and posterior to the anterior superior iliac spine. The median diameters of the nerves measured by ultrasound were: ilioinguinal 3.0x1.6 mm, and iliohypogastric 2.9x1.6 mm. The median distance of the ilioinguinal nerve to the iliac bone was 6.0 mm and the distance between the two nerves was 10.4 mm. CONCLUSIONS: The anatomical dissections confirmed that our new ultrasound-guided approach to the ilioinguinal and iliohypogastric nerve is accurate. Ultrasound could become an attractive alternative to the 'blind' standard techniques of ilioinguinal and iliohypogastric nerve block in pain medicine and anaesthetic practice.

Estimation of pelvic tilt on anteroposterior X-rays--a comparison of six parameters

OBJECTIVE: To compare six different parameters described in literature for estimation of pelvic tilt on an anteroposterior pelvic radiograph and to create a simple nomogram for tilt correction of prosthetic cup version in total hip arthroplasty. DESIGN: Simultaneous anteroposterior and lateral pelvic radiographs are taken routinely in our institution and were analyzed prospectively. The different parameters (including three distances and three ratios) were measured and compared to the actual pelvic tilt on the lateral radiograph using simple linear regression analysis. PATIENTS: One hundred and four consecutive patients (41 men, 63 women with a mean age of 31.7 years, SD 9.2 years, range 15.7-59.1 years) were studied. RESULTS: The strongest correlation between pelvic tilt and one of the six parameters for both men and women was the distance between the upper border of the symphysis and the sacrococcygeal joint. The correlation coefficient was 0.68 for men (P<0.001) and 0.61 for women (P<0.001). Based on this linear correlation, a nomogram was created that enables fast, tilt-corrected cup version measurements in clinical routine use. CONCLUSION: This simple method for correcting variations in pelvic tilt on plain radiographs can potentially improve the radiologist's ability to diagnose and interpret malformations of the acetabulum (particularly acetabular retroversion and excessive acetabular overcoverage) and post-operative orientation of the prosthetic acetabulum.